U.S. Pat. No. 4,672,501 entitled "Circuit Breaker and Protective Relay Unit" describes the use of a digital circuit interrupter employing a microprocessor in combination with ROM and RAM memory elements to provide both relaying as well as protection function to an electrical distribution system.
U.S. Pat. No. 4,833,563 entitled "Molded Case Circuit Breaker Actuator-Accessory Module" describes an integrated protection unit that includes basic overcurrent protection facility along with selective electrical accessories. A specific actuator-accessory module is selected to give the required accessory function along with basic overcurrent protection. This patent supplies a separate shunt trip signal directly to the actuator-accessory module without connection to the circuit breaker trip unit circuit.
U.S. patent application Ser. No. 08/247,198 filed May 20, 1994 entitled "Digital Circuit Interrupter Shunt Trip Module" describes an integrated circuit breaker having shunt trip capability along with automatic overcurrent protection. The shunt trip unit provides auxiliary power to the trip unit and allows the trip unit to report and record the shunt trip operation.
When a shunt trip signal is generated, it is important to determine whether there is sufficient operating power to operate the circuit breaker actuator to initiate the circuit breaker contact separation as well as determining whether the circuit breaker contacts are already separated.
The subject invention proposes a shunt trip control circuit that interacts with the circuit breaker trip unit to provide shunt trip circuit interruption whether the signal processor within the trip unit is operational or not.